The invention relates to a manually operated locking device of a seat belt retractor for vehicles where the winding shaft is usually urged to retract the webbing, but automatically prevented from rotating in such a direction as the webbing may be paid out at a time of, for example, a sudden deceleration of a vehicle.
In a seat belt retractor, the webbing is connected at one end to a retractor to be wound by a spring. In an emergency such as a collision or a sudden velocity change of the vehicle, an automatic locking means is actuated by means of an inertia sensing means to prevent the protraction of the webbing from the retractor so as to restrain the occupant in the seat for safety.
In this situation, the webbing is normally allowed to be paid out from the retractor except for the time of the emergency so that the occupant may arbitrarily change driving posture during the normal running of the vehicle.
In this manner, because of the free protraction of the webbing from the retractor during the normal running of the vehicle, in cases where a baggage, an infant or child seat is fastened to the seat by means of said webbing, the baggage or the like becomes liable to give the webbing a stress for gradual protection under the influence of the inertial force developed owing to the starting acceleration, stopping deceleration or centrifugal force at the time of normal turning so that the webbing possibly fails to restrain said baggage or the like in the seat.